Protective effects of household-based TB interventions are robust to neighbourhood-level variation in exposure risk in Lima, Peru: a model-based analysis.

Abstract

Untargeted active screening and treatment programmes for tuberculosis (TB) have not been shown to be more effective than passive screening and isoniazid preventive therapy (IPT) for reducing TB incidence. In this manuscript, we compare the efficacy of targeting screening and IPT on high-risk household contacts of diagnosed TB cases, with less-targeted active screening approaches in Lima, Peru. We conducted a population-based prospective cohort study within households of TB cases in Lima. We identified all adults diagnosed with incident pulmonary TB from 2009 through 2012 at 106 participating public health centres (HC) within our catchment area of ∼3.3 million inhabitants. We estimated combined effects of community and household exposure on the risk of latent TB infection (LTBI) and incident TB disease. We used simulation modelling to assess the efficacy of TB screening programmes for reducing the risk of incident TB in these contacts. Individuals with household exposure to TB are more likely to present with LTBI and TB disease than those without this exposure, despite wide variation in community exposure. Simulations suggest that more cases are prevented by 1000 administrations of IPT to tuberculin skin test (TST)-positive household contacts of identified TB cases (30, 95% CI = 16,47) than from blanket screening and treatment in the community (7, 95% CI = 2,17). Household exposure remains a major driver of incident TB risk among household contacts of identified TB cases. Targeting interventions on these individuals is likely to prevent more cases of TB than blanket screening of individuals in the community.